Experimental and Numerical Study of AISI 4130 Steel Surface Hardening by Pulsed Nd:YAG Laser

Laser surface transformation hardening (LSTH) of AISI 4130 was investigated by a Nd:YAG pulsed laser. Laser focal height (LFH), pulse width (LPW), scanning speed (LSS), and power (LP) varied during the experiments. The microstructure of the treated zone was characterized by optical (OM) and field emission scanning electron microscopy (FESEM). Micro-hardness was measured in the width and depth directions. Results showed that the hardness and depth of hardened layer increased by decreasing the LSS and the laser focal position (LFP), and by increasing the LPW. The results were compared with those obtained by furnace heat treatment of the same steel. Eventually, a finite element model was employed for the simulation of the LSTH of AISI 4130 steel and calculation of the heat-treated zone. The results showed that the model can predict with accuracy the temperature profile and the size and the shape of the laser hardened region.